Have you taken them to a vet to do a fecal? It is possible that the one is sick, though depending on where you got them from the liklihood of this varies. My first inclination would be that "Baby B" the not eating one, is intimidated by "Baby A". Just removing Baby A from the equation for a short time may not solve this, if Baby B has been intimidated for a bit it may not trust that baby A won't jump out and beat it up for eating.
Be very careful with babies that are not eating, this can escalate quite quickly into a serious condition, specifically due to the dehydration that can occur.
If you got them from a reputable breeder I would strongly recommend given them a call and asking their advice.
Good Luck with your babies, and please keep us posted!
Elizabeth
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1.0 Uro Archimedes
0.0 Fish
0.1 Sulcata Minnie
1.1 Iguanas Flik and Loki
0.1 Newfoundland Jasmine
0.1 Feline Winter
Indiana & Wisconsin